Comparative evaluation and co-relation in variation of curve of Spee and curve of Wilson in Class II div. 1, Class II div. 2, and Class III as against Class I malocclusion in central India population- an in vitro study

Introduction Getting acceptable cosmetic results in the soft tissues of the face serves as the foundation for orthodontic treatment planning. Also, in order to achieve healthy static and dynamic occlusal interactions, the teeth must be positioned within the basal bone at the correct position, angle, and inclination. To avoid periodontal issues, provide stability, and achieve a functional occlusion, it is essential to ascertain the individual’s dental arch form before starting of treatment and thus to utilise the mechanics that follow throughout the treatment. Objectives To evaluate and compare variation in Curve of Spee and Curve of Wilson in Class II Div.-1, Class II-Div-2 and Class-III as against Class I malocclusion in central India population. Methodology Irreversible hydrocolloid impression will be taken with perforated metal stock trays and stone cast will be poured. This will be scanned using CAD CAM machine and curve of Spee and Wilson will be measured using reverse engineering. Expected Result It will assist us in treatment planning for preventing periodontal issues, assuring stability, and achieving functional occlusion by evaluating and comparing the Spee and Wilson curves in Class II Divison-1, Class II Divison-2, and Class-III malocclusion with Class-I malocclusion. Conclusion Every single patient receiving orthodontic treatment has the COS, which is crucial to achieving a stable occlusion. Almost every patient who receives orthodontic treatment eventually experiences the Spee Curve. Since there aren’t many studies examining the relationship between the Curves of Spee and Wilson, their impact on dentoskeletal morphology, and their role in occlusal stability.


Introduction
Getting acceptable cosmetic results in the soft tissues of the face serves as the foundation for orthodontic treatment planning.Also, in order to achieve healthy static and dynamic occlusal interactions, the teeth must be positioned within the basal bone at the correct position, angle, and inclination.To avoid periodontal issues, provide stability, and achieve a functional occlusion, it is essential to ascertain the individual's dental arch form before starting of treatment and thus to utilise the mechanics that follow throughout the treatment.

Objectives
To evaluate and compare variation in Curve of Spee and Curve of Wilson in Class II Div.-1, Class II-Div-2 and Class-III as against Class I malocclusion in central India population.Irreversible hydrocolloid impression will be taken with perforated metal stock trays and stone cast will be poured.This will be scanned using CAD CAM machine and curve of Spee and Wilson will be measured using reverse engineering.

Expected Result
It will assist us in treatment planning for preventing periodontal issues, assuring stability, and achieving functional occlusion by evaluating and comparing the Spee and Wilson curves in Class II Divison-1, Class II Divison-2, and Class-III malocclusion with Class-I malocclusion.

Conclusion
Every single patient receiving orthodontic treatment has the COS, which is crucial to achieving a stable occlusion.Almost every patient who receives orthodontic treatment eventually experiences the Spee Curve.Since there aren't many studies examining the relationship between the Curves of Spee and Wilson, their impact on dentoskeletal morphology, and their role in occlusal stability.

Background and rationale
Planning for orthodontic treatment begins with achieving acceptable cosmetic outcomes in the soft tissues of the face.In order to achieve healthy static and dynamic occlusal interactions, it is also crucial to place the teeth in the basal bone with the correct angulation, inclination, and location.In order to prevent periodontal disease, provide stability, and achieve a functional occlusion, it is critical to identify the patient's dental arch form before commencing treatment so that mechanics can be used to conform arch form throughout the therapy.Periodontal problems in teeth are caused by teeth moved orthodontically that go beyond the basal border and compromise the stability after treatment.The occlusal plane should be flattened and the Wilson Curve should be levelled as the end results of orthodontic therapy. 1 The human dentition exhibits the natural phenomenon known as Curve of Spee (COS).For a successful masticatory system, the anteroposterior curve of occlusion is necessary. 2In 1890, F. Graf von Spee (1855-1937), German anatomist, described the Curve of Spee.He discovered that the occlusion line in skulls with worn away teeth was a line on a cylinder perpendicular to the mandibular incisors' incisal borders, surface of occlusal of 2 nd molar, and the anterior border of the condyle. 3The COS, which is essential to attaining a stable occlusion, is present in every single patient undergoing orthodontic treatment.In orthodontics, the arc that is perpendicular to the incisal margins is currently referred to as the "Curve of Spee". 4 Recent studies have shown that the mediolateral curve plays a biomechanical role in mastication by improving the efficacy of forces of occlusion during mastication and the crush/shear ratio between the posteriors.Dental malocclusions with significant overbites typically have an inflated Curve of Spee. 3 As a result, there will be an inappropriate functional occlusion since the muscle imbalance will be altered.
Wilson was the very first to distinguish the lower grinding teeth's lingual inclination and the higher grinding teeth's buccal inclination.The Curve of Wilson is the name given to this occlusal curve in the coronal plane.The Wilson Curve allows for lateral mandibular excursions without posterior obstructions. 2r adequate function, the amount of buccolingual tooth inclination must be determined and quantified in order to support treatment objectives. 2 The palatal and buccal cusps of the posteriors are in functional contact as a result of this curvature, which appears to necessitate a concave mandibular arch as well as a concave and convex maxillary arch. 5It would be logical to expect that the incline of bone would be oriented in this direction for the best masticatory stress given the alignment of the anatomical parts outlined by Dawson.Okeson outlined the purpose of the Curve of Wilson, which prevents balancing interferences and ensures the most efficient utilisation of cuspal contacts. 2drews came up with 6 keys of normal occlusion out of which 3 rd key is tooth inclination, which is the labiolingual as well as buccolingual inclination of the crown.He saw a lingual tilt in the posterior crowns of the mandible and maxilla. 2 One of the elements included in the six keys to occlusion is the Curve of Spee.According to Andrews, COS in people with proper occlusion varies from flat to moderate. 1 The COS and COW in the lower arches of people living in central India will be determined in this study.In this study, reverse engineering is used to determine the Wilson curve and the Spee curve, which is useful for understanding its comprehensiveness as well as the impact it has on stable occlusion.The measurement and significance of compensatory curves have also been discussed in various studies.
In literatures prior to our study, some of the compensatory curves were shown to be correlated with dentoskeletal malocclusions and normal occlusion.The link between the Curves of Spee and Wilson and their effect on morphology of dentoskeletal, their potential to maintain stability of occlusion have all been the subject of a few studies.This investigation investigates the connection between compensatory curves and how it might aid in the development of treatment plans for specific malocclusions.

REVISED Amendments from Version 2
We have added the reason for not using intraoral scanner directly in the manuscript.

Eligibility criteria
Inclusion criteria: • Patients of age group between 14-30 years.
• Complete permanent dentition except third molars considering it is the tooth that is most frequently lost owing to extraction or congenital tooth loss.
Exclusion criteria: • Patient with previous orthodontic treatment.
• Patient with ongoing orthodontic treatment.
• Patient with missing or impacted teeth.
• Patient with systemic disease.
• Patient with previous record of trauma or surgery.

Intervention
• The study will be conducted on patients coming to the Department of Orthodontics and Dentofacial Orthopedics and diagnosed with Class I, Class ІІ div-1 and Class II div-2 & Class III malocclusion will be selected for the study.
• Written informed consent will be obtained from all the participants.
• Irreversible hydrocolloid impression will be taken with perforated metal stock trays and stone cast will be poured.Due to the lack of an intraoral scanner in our location, we will have to scan the cast instead.This will be scanned using CAD CAM machine which allows us to work on machine-readable measurements and geometry, which is required for our investigation.Curve of Spee and Wilson will be measured using reverse engineering.
Reverse engineering is the practice of disassembling an object in order to discover how it functions.It is generally done to analyze and learn how something functions, although it is frequently used to copy or improve the end result.
• The curve of Spee will be measured by creating a tangent line connecting distobuccal cusp of mandibular 2 nd molars and highest tip of the mandibular incisors in a sagittal section.Measurements will be taken from that tangent line to the deepest point on the premolar region (Figure 1). 6 • Frontal sections will be cut in the area of centre of 1 st molar.We shall follow the axis of molar, which follows a line that connects molars' furcation and occlusal groove, to measure the Wilson curve's angle.The greatest protuberance of the soft tissues present on buccal alveolar crest, the WALA points on the right and left bones, will be used to form a reference line.We can use it to calculate the angle between the left and right molars.The total angulation will be the sum of θ 1 and θ 2 (Figure 2). 5 Outcomes To obtain a functional occlusion, it is essential to identify the patient's dental arch form before the procedure and to apply mechanics that conform with the arch form throughout the therapy.

Sample size
Formula for sample size when comparing two means Where; Zα represents the degree of significance at 5% i.e., 95% Confidence interval ¼ 1.96 Zβ is the test's power ¼ 80% ¼ 0.84 Figure 1.Curve of Spee will be taken from that tangent line to the deepest point on the premolar region.

Statistical method
All the results will be calculated using R version 4.2.3 (Shortstop Beagle).Data for outcome variables will be tested for normality using Kalmogorov-Smirlov.Comparative analysis over the outcome of functional occlusion in different malocclusion will be evaluated and measurement of depth of curve of Spee and Wilson in millimeters respectively.ANOVA will be used to find significant difference in mean in comparison of 4 groups.Tukey test will be used for comparative evaluation of measurement in between 2 groups pairwise.P-value ≤ .05will be considered significant 5% level of significance and 95% confidence of interval.
The results and measurements will be evaluated by experienced technical engineers for Inter-rater reliability test to check the consistency of result obtained.

Dissemination
This protocol will assist us in evaluating and comparing the Spee and Wilson curves in Class II Div-1, Class II Div-2, & Class III malocclusions as against Class-I malocclusions, & this will help us design our treatments in order to avoid periodontal issues, ensure stability, and achieve effective occlusion.

Study status
Not started yet.

Discussion
Dentists may use Spee curve analysis to predict how the occlusion will develop in the sagittal plane.The inclination of the masseter muscle was positively correlated with the Spee curve.The placement of the mandibular posterior teeth with this forward tilt increases the efficacy of the chewing muscles.In Wilson curve, the posterior teeth's inclination is caused by two factors.The first has to do with loading resistance, and the second, with masticatory function. 8veral of the compensatory curves have been linked to normal occlusion and dentoskeletal malocclusions in literature before our study.A few studies have looked at the relationship between the Curves of Spee and Wilson, their impact on dentition, and their capacity to preserve stability of occlusion.This study explores the relationship between compensatory curves and how it might help in formulating treatment regimens for particular malocclusions.This is a comparative study about curve of Spee and Curve of Wilson in malocclusion patients.It is unquestionable the importance of those curves to a healthy occlusion and it is interesting to determine if different malocclusions present different characteristics to be included in the treatment correction planning.Nevertheless some issues seems incomplete and in my opinion need revision: 1.It was not clear if the group with class I malocclusion will be a control group or will be compared as a malocclusion group and so the research will have no control group.My question is based on the fact that class I occlusion not necessarily is a normal occlusion.Conceptually, class I is a malocclusion.

Ethical considerations
2. Considering item 1, it would be a lot more interesting to have a group of normal occlusion as control group and then study curve of spee and curve of wilson deviation from normal occlusion 3. The reference used to create methodology for curve of Wilson analysis use CBCT exams to achieve long axis of mandibular molar.Using cast models, it seems difficult to be sure about the exact localization of root furcation.I encourage authors to change curve of wilson determination methodology.
Is the rationale for, and objectives of, the study clearly described?Partly

Are sufficient details of the methods provided to allow replication by others? Yes
Are the datasets clearly presented in a useable and accessible format?Not applicable

Are sufficient details of the methods provided to allow replication by others? Not applicable
Are the datasets clearly presented in a useable and accessible format?

Not applicable
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Orthodontics and dentofacial orthopedics I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

Is the study design appropriate for the research question? Yes
Are sufficient details of the methods provided to allow replication by others?Yes

Are the datasets clearly presented in a useable and accessible format? Yes
Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Sleep dentistry, preventive dentistry, cephalometric analysis
We confirm that we have read this submission and believe that we have an appropriate level of expertise to confirm that it is of an acceptable scientific standard." corresponds to the steps followed in the procedure of the study, not the aims of the study.Perhaps it would be better to state that the study will identify the relationship between the Spee curve and the Wilson curve for each malocclusion type.

1.
It is not clear if the measurements will be done by one or more observers; if so, it should be specified that an interrater reliability test will be performed and information regarding the observers experience in the field.

2.
Explain the lack of a direct 3D scan of the patients, and keep in mind the differences in accuracy between direct scanning and cast model scanning.

3.
In the Introduction section, where there is the following statement:" The occlusal plane should be flattened and the Wilson curve should be levelled as the end results of orthodontic herapy," reference number 2 is used incorrectly.The author who made that original statement corresponds to [1] Please correct.

Ruchika Pandey
Thankyou sir for your thorough analysis of my article.I have made the following changes based on your review.Response-I have done the necessary changes.

2.
It is not clear if the measurements will be done by one or more observers; if so, it should be specified that an interrater reliability test will be performed and information regarding the observers experience in the field.
Response -I have specified about interrater reliability test.
3.Explain the lack of a direct 3D scan of the patients, and keep in mind the differences in accuracy between direct scanning and cast model scanning.
Response -Regarding the lack of a direct 3-D scan of the patient, scanning intraorally will provide a more accurate result, however due to the unavailability of an intraoral scanner in our location, we will have to scan the cast instead.We will do our best to eliminate distortion while taking and pouring the impression cast.Competing Interests: No competing interests were disclosed.
The benefits of publishing with F1000Research: Your article is published within days, with no editorial bias • You can publish traditional articles, null/negative results, case reports, data notes and more • The peer review process is transparent and collaborative • Your article is indexed in PubMed after passing peer review • Dedicated customer support at every stage • For pre-submission enquiries, contact research@f1000.com MemorialInstitute of Dental Sciences, Mangalore, India Dinesh Rao, AB Shetty Memorial Institute of 3.

•••
To evaluate Curve of Spee and Curve of Wilson in Class II Div.-1, Class II Div.-2 and Class-III malocclusion in central India population.To evaluate Curve of Spee and Curve of Wilson in Class-I malocclusion in central India population.To compare variation and relationship between Curve of Spee and Curve of Wilson in Class II Div.-1, Class II Div.-2 malocclusion and Class-III as against Class I malocclusion in central India population.Trial design: In-vitro study Protocol Study setting Following study will be done at the Department of Orthodontics and Dentofacial Orthopedics, Sharad Pawar Dental College, Sawangi (M), Wardha, in cooperation with the Department of Prosthodontics.

Figure 2 .
Figure 2.With WALA point used as a reference line Curve of Wilson will be measured.
Velandia Palacio 1 CICO, Institución Universitaria Colegios de Colombia UNICOC, Bogotá, Colombia 2 CICO, Institución Universitaria Colegios de Colombia UNICOC, Bogotá, Colombia 3 CICO, Institución Universitaria Colegios de Colombia UNICOC, Bogotá, Colombia The article underscores the significance of the Curve of Spee (COS) and Curve of Wilson (COW) in relation to occlusion and mastication, as well as their biomechanical functions.It further explores the correlation between these curves and dental malocclusions, their influence on treatment planning, and their connection to dentoskeletal morphology and occlusal stability.The aim of the study is to investigate the connection between compensatory curves and how it might aid in the development of treatment plans for specific malocclusions .I would like to point out the following in my review of this manuscript: The objectives are "to evaluate the curve of Spee and the curve of Wilson in Class II Div.-1, Class II Div.-2, and Class-III malocclusion in the central Indian population.To evaluate the curve of Spee and the curve of Wilson in Class-I malocclusion in the central Indian population.

1 .
The objectives are "to evaluate the curve of Spee and the curve of Wilson in Class II Div.-1, Class II Div.-2, and Class-III malocclusion in the central Indian population.To evaluate the curve of Spee and the curve of Wilson in Class-I malocclusion in the central Indian population."corresponds to the steps followed in the procedure of the study, not the aims of the study.Perhaps it would be better to state that the study will identify the relationship between the Spee curve and the Wilson curve for each malocclusion type.

4 .
In the Introduction section, where there is the following statement:" The occlusal plane should be flattened and the Wilson curve should be levelled as the end results of orthodontic herapy," reference number 2 is used incorrectly.The author who made that original statement corresponds to [1] Please correct.Response -I have done the correction.

Peer Review Current Peer Review Status: Version 2
Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Is the rationale for, and objectives of, the study clearly described? Partly Is the study design appropriate for the research question? Yes Are sufficient details of the methods provided to allow replication by others? Yes Are the datasets clearly presented in a useable and accessible format? Not
applicableCompeting Interests: No competing interests were disclosed.